Hello and welcome to Grand
Canyon National Park.
My name is Ranger Jabez.
Today I'm out here standing at Pima Point.
Have you ever wondered how the
Grand Canyon was formed and why it is
Found here in Northern Arizona?
These are some commonly asked
questions that we get from visitors.
To understand the formation of the canyon,
there is a simple way to sum
up how it shaped over time.
All you have to remember
are the letters D U D E or dude.
The first letter stands for deposition.
The Earth is made out of igneous,
metamorphic, and sedimentary rocks.
Here at the Grand Canyon,
the majority of rocks are sedimentary.
If you look into the Canyon you can
see the different layers of rocks
over hundreds of millions of years.
Different types of sediments were
deposited to make the collections
of layers that we see today.
Each of these layers tells us a
story of the environment that
existed when they formed.
Some are made up of oceanic sediment,
when this area was covered by a shallow sea.
While others reflected a drier climate
characterized by windswept sand dunes.
These differing conditions give the
rocks a unique layer cake look.
Most of this deposition occurred
around sea level,
but I'm not underwater, anywhere near a sea.
In fact,
the South Rim of the Grand Canyon where
I'm standing is 7000 feet above sea level,
which brings us now to the next letter.
U stands for uplift.
What helps account for Grand Canyon's
elevation. 50 to 70 million years ago the
earth's tectonic plates began to shift,
causing his uplift.
Two plates collided, which forced
one underneath the other, pushing
this area up in a flat,
uniform fashion, creating the
Colorado Plateau. Most of the time.
plates collide in a more violent manner,
creating valleys or mountains;
but the relatively calm,
uplifting this area kept those rock
layers, from our first step, in place.
Now with their region high and flat,
the stage is set for our
next letter in our process.
The second D is for downcutting.
This process began about five to six
million years ago when the Colorado
River began to flow its current course.
You might wonder how that tiny
river that you see from the rim
help carve this massive canyon.
Water is more forceful when
it has a steeper slope.
The Colorado River starts around
14,000 feet in elevation and drops
about 7 feet per mile over its course.
As it flows,
it carries with a large amount of
debris that act as liquid sandpaper
- as it moves across the relatively
soft sedimentary rocks of the canyon.
This explains
the deep cut that helped to
create the canyon.
However, other forces
contributed to make it so grand,
which takes us to our last letter.
The E stands for erosion.
What the river downcutting other forces
helped in the shaping of the size of
the Canyon. Water was still a factor,
but in the forms of rainfall,
ice wedging, and snow melt.
Ice wedging is when water freezes and
thaws in the cracks of the canyon.
This type of erosion occurs here
because the huge temperature swings
that we get throughout the year.
During the day, it can be warm but
at night the temperatures can drop
below freezing. Water freezes and
thaws in the cracks of rocks causing
them to break apart from the sides
of the canyon and fall to the bottom.
Other types of erosion occur
from snowmelt and rainfall.
There are two wet seasons here at the canyon.
One is in the winter, when it snows
and the other is monsoon season.
during the summer months.
The North Rim gets more snow and
rainfall than the South Rim.
based on the difference in elevation.
It's about 1000 feet higher.
When the snow melts,
or when the rain falls on the
South Rim, it tends to flow away
from the canyon. On the North Rim,
it tends to flow into the canyon.
Because of this,
the walls on the North Rim are
eroding further away from the river.
Thanks to water's contribution
to the forces of erosion,
we can enjoy this grand site
and marvel in its glory.
We want to thank you for watching
and we hope one day you can come
visit Grand Canyon National Park.
And if you do remember D U D E or dude.